The U.S. Navy is accompanying U.S.-flagged ships through the Strait of Hormuz to ensure they are not harassed by Iranian forces, and is in talks to extend the same protection to other nations' vessels, U.S. officials say.

U.S. Navy ships accompanied four U.S.-flagged ships and a British vessel through the strait at the mouth of the Persian Gulf on April 30

The cautionary measures follow Iran's seizure of the cargo ship Maersk Tigris and harassment of another commercial vessel in the last week.

The Marshall Islands-flagged Maersk ship is still being held by Iran, which cites a commercial dispute as its reason..

U.S. Pentagon spokesmen say they will offer protection "indefinitely" to civilian ships going through the maritime chokepoint, a crucial oil route, under an operation approved by Defense Secretary Ashton Carter.

"Our current plans are for accompanying US-flagged ships, although there are discussions with other nations to include their vessels as well," Central Command spokesman Colonel Patrick Ryder told reporters on May 1.